Coil resistance change

[Justadude]

Both atties that have nichrome coils are going from low (when hot) to high (when cool) in resistance.

Kanthal coil doesn't seem to do do that.

Can one of you guys confirm on your set up that that's normal on your end as well? (Assuming you're using nichrome)

Btw none of the ones I've tested had wick in them.

 

[TheRac25]

But half an ohm? Isn't that too big of a difference?

0.038 is over 10 times less than half an ohm
i think the metal expansion is causing it somehow

 

[Justadude]

0.038 is over 10 times less than half an ohm
i think the metal expansion is causing it somehow

Oh yeah cause I'm already in the 10ths of an ohm

So nichrome expands when it gets hotter?

 

[Alien Traveler]

Oh yeah cause I'm already in the 10ths of an ohm

So nichrome expands when it gets hotter?

Everything expands with temperature…

Nichrome is protected from air with chromium oxide and kanthal – with aluminum oxide. Aluminum oxide is much better insulator. So, may be (just may be) your coils expand when hot and nichrome coil (protected with weaker insulator) shortens in between wires. If you wish you can try to make loose coil, if I am right it should not change resistance more that kanthal coil (they have pretty low and similar temperature coefficient).

By the way, when you fire coil without wicks and let it glow red, its temperature is about 1200 F, if it is bright yellow then temperature is 1900 F. With saturated wicks coil temperature should stay below 550 F (VG boiling point). Quite a difference. May be weird behavior of your coils will be not so pronounced when vaping.

 

[Justadude]

Everything expands with temperature…

Nichrome is protected from air with chromium oxide and kanthal – with aluminum oxide. Aluminum oxide is much better insulator. So, may be (just may be) your coils expand when hot and nichrome coil (protected with weaker insulator) shortens in between wires. If you wish you can try to make loose coil, if I am right it should not change resistance more that kanthal coil (they have pretty low and similar temperature coefficient).

By the way, when you fire coil without wicks and let it glow red, its temperature is about 1200 F, if it is bright yellow then temperature is 1900 F. With saturated wicks coil temperature should stay below 550 F (VG boiling point). Quite a difference. May be weird behavior of your coils will be not so pronounced when vaping.

That actually stands true. When I fired it up when wicked and saturated it wouldn't drop below .125 which is not too big of a difference from .144 where it's sitting at when cooled off.